Lens antenna system



Feb. 4, 1958 w. slcHAK ET AL 2,822,541

LENS ANTENNA SYSTEM Filed Dec. l0. 1954 5 Sheets-Sheet l INVENTORS /4 WMU/1M s/c//AK ATTORNEY Feb. 4, 1958 W. SICHAK ET AL LENS ANTENNA SYSTEM Filed Dec. 1o. 1954 3 Sheets-Sheet 2 INVENTORS ATTGRNEY Feb. 4, 1958 w. slcHAK ET AL 2,822,541

LENS ANTENNA SYSTEM Filed Dec. l0. 1954 5 Shee'ts-Sheet 5 INVENTORS WML/AM .S/CHAK EO W//V WEST/QOOK ATONY power dividing junctions. Ytion was in itself negligible, yet the sum of the losses of LENS ANTENNA SYSTEM William Sichak, Lyndhurst, kand Edwin P. Westbrook Nutley, N. J., assignors to .International Telephone and TelegraphV Corporation, Nutley, N.Y J., a .corporation of/Maryland Application December 10, 1954, Serial -No.:474,`359

"14 Claims. (Cl. 343-783) Y VThis invention relates todirectional antennasystems ,and more `particularly toy antennas of 'the lens type and arrays lthereof particularly useful in transmission and reception of radio frequency `energy in lthe microwave region.

Efforts have been made heretofore to provide high resolution Vantenna arrays, such that the beam width is less than about one degree. lSuch arrays are generally used with a separate reflector to produce the desired vertical pattern,`generally cosecant. The advantages of the arrayreflector combination over the single fed antenna-reflector combination are that Yseparate control of the azimuth and `elevation kpatterns are possible, the reflector may comprise a simple `cylindrically curved member and better control is obtained of polarization. The main disadvantage, however, is ,the greater complexity of the feeding systemfor ,the array.

To obtaina linear array it has been proposed heretofore to .employan end-fed waveguide or coaxial .line `provided with slots and/ or dipoles, or a pill box. ln. end-.fed

arrays, vthe diiculties experienced are shift `of beam.with

frequency, mutual impedance betweenadjacent:slotsand the klarge'number of slots required. The pill box or `sectoral lens is objectionable because of its largesize and weight.

.In the copending application of W. Sichak, Serial No.

l 332,424, tiled January 21, 1953, a linear arra-yis .disclosed all the junctions resulted in sufHcient radiation to produce :undesirable side lobes.

One of the objects of this invention is to provide such an array with means to eliminate or greatly minimize the aforementioned `side lobes; and another object is to provide a new array capable of covering a corresponding 4frequency band wherein the number of radiation units -andgpowerdividing junctions are greatly reduced.

Still another object is to provide a new lens type of antenna having highly directive characteristics; Vand V*a Vfurther object is to provide an improved linear arrayiemploying lens antennas.

One of the features of the invention'is a simplified type of lens antenna comprising two spaced parallel planar conductors and a layer of dielectric material tilling the space between the conductors, the forward edge of the dielectric layer being arcuately curved in a plane parallel to said planar conductors to focus radio frequency energy propagated therethrough.

Another'feature is the arrangement of such lens `anes Patente() f' 2,822,541 l'Patented eb. 4, 1958 .f tion carried on the dielectric layer and the curved forward edgeof Vthe dielectric layer adjacent said'tapered section.

.Each .tapered section of the .arrayfisfed .by a conductor strip allsocarlriejd` bylthe dielectric layer in closely spaced parallel` relatioutotheplanar conductor whereby radio 'frequency .energy isfgu'ided` by the strip in .conjunction with the planar jsurfacel of theplanar conductor. To .eliminate .orat-'Jeast minimize `radiation from the power v`dividing junctions'feeding. the strips, a second planar con- .ductor.is'.disp,osed in overlying spaced lshielding relation- `ship to .the Yantennasections, the individual feeders andthe powendividingjunctions. coupled thereto. YEach vlens `.portion of .theantennaarray is such'as to accomplish-the sarne radiation normally.obtainedV by eightof Ythe antennas in the :aforementioned model. By employing lens antennasgofthe ...character `herein disclosed the number rof powerdividing junctionsis .greatly,decreased.

U.accompanying drawings', in which:

'Iheabove-mentionedand other features and objects lofthis .inventionewill'become .more apparent by reference `tothezfollowing description taken in conjunction with th Fig. 1 .isa view in perspective .of anantenna array made in accordance-withthe principles of this invention;

Figs. 2 and Bfare sectional views taken along lines 2 2 :and 3-3 of Fig. 1;

Eig. 4 is aviewninplan showingan-array of antenna units'inwhich each antenna is provided witha parabolic antenna;

Fig. 5 is a cross-sectional view taken along-5=5 ..of'one of the antenna-.parabolic reflectorunits shown in Fig. 4;

Fig. 6 is a view in perspective of another embodiment of the invention-showing Van antennaarray; and

Fig. -7 is a sectional view taken lalong line 7-7 of Fig. 6.

AReferring to Figs. 1, 2 and 3.a :linear `arrayrisillus- '.trated employing "four lens gantennas. fflhe'construction vtof the antennas and the -waveguidefeeder thereto Visjibased on the lineabove'ground or Microstrio-type `offwaveguide, comprising a first or planar: conductor 1 Tand asecond or line conductorz spaced-apart by a vthin strip or Slayer of dielectric material 3. The two conductors 1 and `23 are preferably of flat strip materialfthe,planar conductor being wider than the line conductor so -that propaga- :tion ofmicrowaveenergy therealong is in a mode simiv Vthicknessof the pspacingdielectric 3. The 'dielectric-may Vlayerlas indicated `at1'11. .lnonefullsize :modelbuilt for S9000 me'gacycles the width L of the Ylens aperturem was eight inches while the focal length was nine inches.A

tapered sections interconnecting such sections in al common. sheet 12 and angling the sheet outwardly from the plane of the tapered sections so as to form a horn effect in conjunction with a similarly angled portion 14 formed of the forward extension of the planar conductor 1. Such a horn structure enhances the directiveness of the broadband linearv array. A one-surface cylindrical lens 15 maybe disposed between the angled portions 13 and 14 with the one-surface face thereof spaced a desired distance from the forward edge of the dielectric 3. The curvature ofthe lens face may either be concave or convex, the particular curvature being such as to provide the focus effect desired. For design information, reference may be had to pages 388-4l2 on Dielectric and Metal-plate Lenses by I. R. Risser in volume 12 of the Radiation Laboratory Series of i949.

While the lens antenna array illustrated in Fig. l ernploys only three power dividing junctions and, therefore, minimizes greatly the side lobe effect heretofore experienced with a corresponding 32 antenna array, the radiation pattern may have the side lobe effect entirely eliminated by providing a conductive shield in overlying relationship to the tapered sections and the feeder arrangement therefor. Such a shield is shown by a second planar conductor 16 which is Aextended rearwardly from the angled section 13 in overlying spaced Vrelation to the tapered section 4 7 and the power dividing junctions 8,

I v9 and 10. While Vthe dielectric spacing between the conductive strips forming the feeders and tapered sections of the antennas and the planarV conductor 1 is in'the order of ,onefeighth inch, the spacing of the shield 16 above the strip material is preferably in the order of one-quarter inch or greater. The provision of this conductive shield over the power dividing junctions of the 32 antenna array was also found to Veliminate the undesired side lobes hereinbefore referred to.Y v

In Figs. 4 and 5, an array of single radiator units A to N is disclosed, yeach unit being built in a manner similar to thatdescribed in connection with the antenna units illustrated in Figs. 1, 2, and 3. In Figs. 4 and 5 the single antenna unit comprises a tapered conductive strip 17 disposed in dielectrically spaced relation to a planar conductor 18, a layer of dielectric material 19 tilling the space therebetween. The tapered section 17 is fed by a strip 20 one end of which is connected to the small end of the tapered section and the other end of which is terminated in overlying relation to an opening 21 formed in the planar conductor 18. A coaxial Wavev guide is coupled thereto by the outer conductor 22 being connected to the planar conductor about the opening 21 with the inner conductor 23 extending through the opening for connection to the strip conductor 20. The forward edge of the dielectric material 19 is arcuately shaped as indicated at 24 along with the forward edge of the sector 17. This curved edge of the dielectric material and the conductor 17 provides a lens effect on the radio frequency energy propagated through the dielectric body. Where the antenna is used for transmission the radio frequency energy is fed through the coaxial waveguide to the lens antenna where it is `radiated toward a parabolic reector 25 carried by an extension 26 of the planar conductor 1S. By suitably shaping and disposing the reflector 25 radiation in the desired direction is obtained.

, ment shown in Figs. 6 and 7 is the arrangement of the V parallel-plate type similar to that described on. page 403 of the aforementioned Volume 12 of the Radiation Laboratory Series. It will be understood, of course, that this lens 27 may also be used in the embodiment shown in Figs. 1 3, and if desired, the lens 15 may be used in the embodiment shown in Figs. 6 and 7. It will also be understood by those skilled n the art that a twosurface lens may be used if desired in place of the one-surface lenses here illustrated.

While we have described above the principles-of our invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of our invention as set forth in the objects thereof and in the accompanying claims.

VWe claim:

l. A lens antenna for radio frequency waves comprising a waveguide having first and second strip conductors and a layer of dielectric material disposing said conductors in parallel spaced relation, said first conductor being wider than said second conductor to present thereto a v planar conducting surface for propagation of radio fre- -quency energy therealong in a mode approximating the TEM mode, said second conductorbeing ared adjacent n the end thereof in a plane parallel to said planar surface and said layer of dielectric being terminated adjacent said liared portion with its forward edge arcuately shaped in a plane parallel to said planar surface to produce a l focusing effect on radio frequency energy propagated therethrough.

2. A lens antenna according to claim l, wherein said rst strip conductor extends beyond the forward edge of said layer of dielectric material and is provided with a parabolic reflector disposed at right angles to the plane of said second conductor, the face of said parabolic reector being disposed toward said layer of dielectric material to reflect radio frequency energy propagated through l said layer of dielectric material.

' TEM mode, a coaxial line comprising inner and outer conductors, said first conductor having an opening therethrough in underlying relation to said second conductor,

`means, couplingsaid coaxial line'to said waveguide with the outer conductor connected to said first conductor about said opening and the inner conductor extending through said opening'and connected to said second conductor, said second conductor being'flared adjacent the output end thereof and said layer of dielectric being terminated adjacent said flared'portion with its forward edge arcuately shaped in a .plane parallel to said planar surface to'provide a focusing effect upon radio frequency energy propagated therethrough, said first conductor being extended beyond said layer of dielectric material and provided with a parabolic reflector disposed at right angles to the plane of said surface to reflect wave energy propagated through said layer of dielectric material.

4. A lens antenna for radio frequency waves comprising'a waveguide terminated in two spaced parallel planar conductors and a'body of dielectric material lling the space between said planar conductors, the forward edge of said dielectric body being arcuately shaped in a plane parallel to said planar conductors whereby the refraction characteristics of said body provides a focusing effect upon radio frequency waves propagated therethrough, a horn-like portion having two opposed walls angled outwardly with respect to the planes of said planar conductors forwardly of the forward edge of said body, and a lens disposed between said angled walls with the curved surface of said lens being spaced a predetermined distance forward of said dielectric body.

5. An antenna array for radio frequency waves comprising two spaced parallel planar conductors, a layer of dielectric material lling the space between said planar conductors, one of said conductors having adjacent portions each tapered rearwardly of the forward edge of said dielectric layer to form in conjunction with the other of said planar conductors a plurality of independent waveguide feeders, the forward edge portion of the dielectric layer forward of each tapered section being arcuately curved to focus radio frequency energy propagated therethrough.

6. An antenna array according to claim 5, wherein said plurality of independent waveguide feeders are coupled to a .common waveguide feeder for division of wave energy from said common waveguide feeder to said plurality of tapered portions, said waveguide feeders each comprising a conductor strip spaced parallel to the planar conducting surface of said other planar conductor whereby wave energy is propagated between said strip and said planar surface in a mode corresponding approximately to the TEM mode.

7. An antenna array according to claim 6, wherein said planar conductors extend beyond the forward edge of said dielectric layer and at an angle outwardly from the plane of said conductors, said second conductor having a planar extension extending backwardly in spaced overlying shielding relation to said tapered sections and said individual waveguide feeders.

8. An antenna array according to claim 6, further including a third planar conductor disposed in spaced overlying shielding relation to said individual waveguide feeders and the coupling thereof to said common waveguide feeder.

9. An antenna array for radio frequency waves cornprising a waveguide terminated in two parallel planar conductors, a layer of dielectric material filling the space between said planar conductors, one of said conductors having adjacent portions tapered rearwardly of the forward edge of said dielectric layer to form in conjunction with the other of said planar conductors a plurality of independent waveguide feeders, the forward edge portion of the dielectric layer forward of each tapered section being arcuately curved to focus radio frequency energy propagated therethrough, and a horn-like portion having two opposed walls of conductive material angled outwardly with respect to the planes of said planar conductors forwardly of the forward edge of said body.

10. An antenna array according to claim 9, wherein said horn-like portion includes a lens disposed between said two walls spaced a given distance forwardly of the arcuately curved edge portions of said dielectric layer.

l1. An antenna array according to claim 9, wherein said plurality of independent waveguide feeders are coupled through coupling connections to a common waveguide feeder for division of wave energy from said common waveguide feeder to said plurality of tapered portions, said waveguide feeders each comprising a conductor strip spaced parallel to the planar conducting surface of said other planar conductor whereby wave energy is propagated between said strip and said planar surface in a mode corresponding approximately to the TEM mode, and a third planar conductor extending rearwardly of one of said walls in spaced overlying shielding relation to said tapered portions, said individual waveguide feeders and the coupling connections between said individual and said common waveguide feeders.

12. An antenna array for radio frequency waves cornprising a first planar conductor, a layer of dielectric material overlying said planar conductor, an array of conductor elements carried by said layer, said array of elements lying in a common plane parallel to said first planar conductor and spaced therefrom a small fraction of a quarter wavelength, a conductor strip coupled to each of said elements extending rearwardly in parallel spaced relation to the planar surface of said first conductor to form in conjunction therewith a plurality of independent waveguide feeders, a common waveguide feeder, means coupling said independent waveguide feeders to said cornmon waveguide feeder, and a second planar conductor disposed in overlying shielding relation to and at least a quarter wavelength above said individual waveguide feeders and the coupling connections thereof to said common waveguide feeder.

13. An antenna array according to claim 12, wherein said elements each includes a at tapered conductive section to which one of said conductor strips is connected and the forward edge of said dielectric layer is arcuately curved adjacent each of said tapered sections to provide a lens effect on the radio frequency energy propagated therethrough.

14. An antenna array according to claim 12 wherein said first and second planar conductors are provided with extensions angled outwardly of the planes thereof and forwardly of said elements, and a lens is disposed between said angled extensions in a given spaced relation with respect to said array of elements.

References Cited in the file of this patent UNITED STATES PATENTS 2,596,190 Wiley May 13, 1952 2,602,856 Rumsey July 8, 1952 2,654,842 Engelmann Oct. 6, 1953 2,669,657 Cutler Feb. 16, 1954 FOREIGN PATENTS 130,548 Australia Dec. 23, 1948 OTHER REFERENCES Wireless Engineer, August 1951, pp. 248-250. 

